IIC EEPROM例程困惑

oy199603 · 发表于 2016-2-29 01:06:33

小弟深夜学习原子哥IIC教程里面讲述的是用IIC读取EEPROM 我最想学的是如何看懂时序表但可惜原子哥只简要的说了几句也给我带来了困惑好了直接上代码

具体也用红笔画出来了我用的是24c02 所以我直接执行ELSE语句 IIC_Send_Byte(0XA0+((WriteAddr/256)<<1));这一句话是和 IIC_Send_Byte(0XA0);
IIC_Wait_Ack();IIC_Send_Byte(WriteAddr>>8)等效的吗？如果等效这个ACK怎么直接没有了？后面两行 IIC_Wait_Ack(); IIC_Send_Byte(WriteAddr%256);
给地址写值地址先取高后取低中间还要ACK？感觉ACK这句话原子哥是随性写的，难道真的有所讲究希望各位有所赐教不然看器件时序图根本写不出代码。
再来一份截图是关于读的这里面的有一些ACK时序图里面根本就没有

xkwy · 发表于 2016-2-29 01:06:34

我仔细按照手册时序图写过AT24C02的驱动代码，

你参考一下，有不懂的再问，

[mw_shl_code=c,true]
static void I2C_Start(void)
{
SDA_OUTPUT = 1;
SCL_OUTPUT = 1;
delay_us(3);

SDA_OUTPUT = 0;
delay_us(1);             /* Thd1 > 0.6us */
SCL_OUTPUT = 0;
}

static uint32_t I2C_Write(uint8_t dt)
{
uint32_t i;
uint32_t re_val;
const uint8_t TB_MASK[] = { (1 << 7),(1 << 6),(1 << 5),(1 << 4),(1 << 3),(1 << 2),(1 << 1),(1 << 0) };

for (i = 0; i < 8; i++)
{
      SDA_OUTPUT = (dt&TB_MASK) ? 1 : 0;

      delay_us(2);          /* Tlo > 1.3us, Tst2 > 0.1us */
      SCL_OUTPUT = 1;
      delay_us(1);          /* Thi > 0.6us */
      SCL_OUTPUT = 0;
}

delay_us(1);             /* Thd2 > 0 */
SDA_OUTPUT = 1;       /* Ensure release signal */

delay_us(2);             /* Tlo > 1.3us, Tst2 > 0.1us */
SCL_OUTPUT = 1;
delay_us(1);             /* Thi > 0.6us */
re_val = SDA_INPUT;
SCL_OUTPUT = 0;

return re_val;
}

static uint8_t I2C_Read(uint32_t respond)
{
uint32_t i;
uint8_t re_val;

SDA_OUTPUT = 1;       /* Ensure release signal */

for (i = 0; i < 8; i++)
{
      delay_us(2);          /* Tlo > 1.3us, Tst2 > 0.1us */
      SCL_OUTPUT = 1;
      delay_us(1);          /* Thi > 0.6us */
      re_val <<= 1;
      re_val += SDA_INPUT;
      SCL_OUTPUT = 0;
}

delay_us(1);             /* Thd2 > 0 */
SDA_OUTPUT = respond ? 1 : 0;

delay_us(2);             /* Tlo > 1.3us, Tst2 > 0.1us */
SCL_OUTPUT = 1;
delay_us(1);             /* Thi > 0.6us */
SCL_OUTPUT = 0;

return re_val;
}

static void I2C_Stop(void)
{
SDA_OUTPUT = 0;
SCL_OUTPUT = 0;
delay_us(3);

SCL_OUTPUT = 1;
delay_us(1);             /* Tst3 > 0.6us */
SDA_OUTPUT = 1;
}

/******************************************************/

extern void AT24C02_init(void)
{
/* SCLB6, SDAB7 */

/* Enable GPIOB Clock */
RCC->APB2ENR |= RCC_APB2ENR_IOPBEN;

/* PB6, PB7: Output, 50MHz, Open-drain */
GPIOB->CRL &= ~((GPIO_CRL_MODE6 | GPIO_CRL_CNF6)
      | (GPIO_CRL_MODE7 | GPIO_CRL_CNF7));
GPIOB->CRL |= ((GPIO_CRL_MODE6 | GPIO_CRL_CNF6_0)
      | (GPIO_CRL_MODE7 | GPIO_CRL_CNF7_0));
}

extern void AT24C02_Write(void *val, uint8_t n, uint8_t Addr)
{
uint8_t *p = val;

I2C_Start();
I2C_Write(0xA0);
I2C_Write(Addr);
while (n--> 0) I2C_Write(*p++);

I2C_Stop();
}

extern void AT24C02_Read(void *val, uint8_t n, uint8_t Addr)
{
uint8_t *p = val;

I2C_Start();
I2C_Write(0xA0);
I2C_Write(Addr);

I2C_Start();
I2C_Write(0xA1);
while (n--> 1) *p++ = I2C_Read(0);
*p = I2C_Read(1);

I2C_Stop();
}
[/mw_shl_code]